Field of the Invention
The present invention relates to a touch sensor integrated type display device, and more particularly, to a touch sensor integrated type display device which is capable of recognizing a user's touch.
Discussion of the Related Art
Various input devices, such as a keyboard, a mouse, a trackball, a joystick, and a digitizer, have recently been used to configure an interface between users and home appliances or various kinds of information communication equipments. However, such input devices as a keyboard or a mouse require the user to learn to use them and take up space, thus making it difficult to improve the completeness of the products. Therefore, the demand for input devices that are more convenient and easier to use and reduce erroneous operations is growing more and more. In response to this growing demand, a touch sensor for enabling a user to input information by directly touching the screen with their hand or a pen was suggested.
The touch sensor is simple to use, has fewer malfunctions, and enables the user to input information without using an additional input device. In addition, the touch sensor can be applied to various display devices because it enables the user to operate it quickly and easily through contents displayed on the screen.
Touch sensors can be classified into an add-on type and an on-cell type. In the add-on type, a display device and a touch panel having a touch sensor are separately manufactured, and the touch panel is attached onto an upper substrate of the display device. In the on-cell type, a touch sensor is directly formed on the surface of an upper glass substrate of a display device.
The add-on type sensor has a structure in which the completed touch panel is mounted on the display device. It has various problems, such as an increased thickness and reduced visibility due to low brightness of the display device.
The on-cell type touch sensor has a structure in which a touch panel is formed on the upper surface of the display device and can have a reduced thickness compared to the add-on type. However, the on-cell type still has the problem of increasing the overall thickness of the display device due to a driving electrode layer, a sensing electrode layer, and an insulation layer for insulating the driving electrode layer and the sensing electrode layer which constitute the touch sensor. This may lead to increased manufacturing costs.
Accordingly, there is a need for a touch sensor integrated type display device capable of solving the problems of the related devices. A touch sensor integrated type display device like the one disclosed in U.S. Pat. No. 7,859,521 is known.
A touch sensor integrated type display device disclosed in U.S. Pat. No. 7,859,521 is able to recognize a touch and a touch position by measuring a change in mutual capacitance caused by touching because common electrodes for display are divided to serve as touch driving electrodes and touch sensing electrodes.
With this configuration, the touch driving electrodes and the touch sensing electrodes are each interconnected by wires according to their functions to avoid contact with different types of electrodes because both the touch driving electrodes and the touch sensing electrodes are formed on the same layer. That is, the touch driving electrodes are connected together through contact holes by touch driving wires, and the touch sensing electrodes are connected together through contact holes by touch sensing wires. This prevents contact between the touch driving electrodes and the touch sensing electrodes.
However, the related art touch sensor integrated type display device has a problem of low aperture ratio because the touch driving wires and the touch sensing wires cross each other in a display area of the display device.
Moreover, the recent increase in the size of display devices has resulted in greater differences in the RC delay (resistance capacitor delay) of the touch driving electrodes depending on their respective positions on a display panel, which in turn resulted in a decreased uniformity of a touch driving signal or touch sensing signal.
FIG. 1 is a view illustrating the decreasing signal uniformity with the increasing size of a display device. As can be seen from FIG. 1, a touch driving pulse Sp has a normal waveform at the input terminal of a display panel DP but a distorted waveform at the far end of the display panel. Also, a sensing signal Ss has a normal waveform near the input terminal but a distorted waveform at the far end. These differences in the waveform make accurate touch sensing more difficult.